TOPIC: 1969 Merc 650 Red Band - lower unit interchange

Hi,

The lower unit on my 1969 Mercury 650 Red Band has a small hole from an impact from previous owner. Ideally I'd like to replace the lower unit: What models interchange with mine? There are plenty up here around Toronto Ontario, I just need to know which one to pick up.

most 650 1965 and up and 6cyl also fit just make sure they are the same gear ratio.

Both 800-4 and 850-4 (along with the later 80hp and 75hp variants) will bolt right up and have the same 2.3:1 gear ratio. I can't recall for sure if yours has the 2.3:1 but I did have a '71 with that ratio and they run very well with those gears.

Craigslist is your friend for spare parts!

Last thought, if the hole isn't in the oil-containing parts of the gearcase, you could have it weld-repaired then repaint.

HTH & G'luck with the replacement.............ed

Hi,

An original 1969 Merc 650 lower unit would have the 2 to 1 ratio. The swap to the later 2.3 to 1 as Ed mention is nice, but a change of the propeller will also then likely be required.

Regards,
Joe
www.fergusonpoolemarine.com
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I think the previous owner had JB weld or something wedged in there and it just came out. The benefit of a new lower unit for me is I get a new skeg, as the one on there right now is really beat up.

I'll look around for the similar year units.

What ratio would I need for the propeller?

I think the previous owner had JB weld or something wedged in there and it just came out. The benefit of a new lower unit for me is I get a new skeg, as the one on there right now is really beat up.

I'll look around for the similar year units.

What ratio would I need for the propeller?

just turn the drive shaft 1 turn and count the turns on the prop shaft. if 1 turn each it is 1-1. if not it will be 2.3-1

Found a decently priced 1979 70HP lower unit. I'm assuming it's compatible, just have to figure out the ratio and prop pitch?

70 hp will not work. They are based not he 4 cylinder and 3 cylinder motors. . You need a big 4 or 6 cylinder lower unit.

Dave B wrote:
"just turn the drive shaft 1 turn and count the turns on the prop shaft. if 1 turn each it is 1-1. if not it will be 2.3-1"

And if you turn the driveshaft two complete revolutions to one for the prop shaft,...You have a 2:1 ratio.

The other thing you need to know is if you have a short shaft (15") or long shaft (20").